Boron compounds containing hydrocarbon radicals, hydrogen and nitrogen, and a process for the production thereof



United States Patent @hliee BEN RADE AELS, HYBRQGEN ANllll NHERUGEN,

TEEEREUF Roland Kiister, Mnlheinr itular), Germany, assignor to Studieugcsellscliait Hobie J1EE (Ruhr),

Germany, a corporation of Germany 4, 1937, f lo. 6%,"833

Claims priority, application Germany lune a, 5. 56 It Claims. ill. Zeb- 563) Thi invention relates to boron compounds containing hydrocarbon radicals, hydrogen and nitrogen, and a pro ess for the production thereof.

It has already been proposed to prepare boron compounds containing hydrocarbon radicals and hydrogen by heating boron compounds of the general formula R 8, in which R represents a hydrocarbon radi al, with hydrogen under pressure at temperatures from 12G-l60 C. According to this prior process, it is theoretically possible completely to hydrogenate the boron hydrocarbons, especially boron alkyls, to form boron hydride B H bi pure E H can only be obtained under spool condition sin e it is known that boron hydride, at high temperatures the region of 180 (1., reacts in a complicated manner with saturated hydrocarbons which are formed in the reaction.

It has now been found that all the hydrocarbon on such boron compounds can be replaced by hydro. without special precautionary measures if addition cornpounds of boron hydride B H in its hypothetical monomeric form 325 are prepared. Accoi to the invention, boron compounds containingl'iydrocarbon rad hydrogen and nitrogen can be produced by heating a boron compound of the eneral formula R E, in which R represents a hydrocarbon radical, preferably an aliphatic hydrocarbon radical, in the presence of a ter" of the general formula NRF.R", in which R, R" R represent hydrocarbon radicals, preferabl' -l aiip. hydroarornatic or aromatic hydrocarbon radicals, hydrogen under pressure at a te store of more than 120 C. N-tribydrocurbon borazanes in which at least one of the hydrocarbon radicals contains two or more carbon atoms are new compounds.

At temperatures higher than 140 C, t pounds of boron tria JlS or other boron and tertiary airlines or the general forn in this equation, each it represents a hydrocarbon radical, preferably an aliphatic, lzydroaromatic or aromatic hydrocarbon radical.

The temperature d l 300 C. or more. When the pr c temperature between 223 and 258 C. ondary reactions occur and t e products is not reduced. it was not to be can c t boron tion temperatures, since it known .1 for example E 5 react in a con l'cated uni'oreseeable rnanncr at temperature hi her than 180 C. with saturated hydrocarbons such as are concurrently formed in the reaction to the invention. (cf. DJ. liurd I. Am. Chem Soc, 70, 2353 (1948)}.

has produced by the procerto unknown are Most of t. e N-trialltyl hora. of the invention whliquid; they have an extraordin in spite of the fact that acccro can be interoreted as bein azl' hypothetical borine l3 so that no complications arise during the production thereof at temperatures up to about 363 Q. This possibility of using a high reaction temperature is a substantial advantage of the process of the invention. It is in fact possible to achieve quantitative conversion to the required borazane within a short time.

In principle, all known boron hydrocarbons can be used. as starting material. It is preferred to use boron trialltyls, which can now be produced very easily from the corresponding aluminum trialkyls. The process of the invention can be carried out without solvents, or in the orescnce of an inert solvent, for example in the presence of a saturated al.'phatic or aromatic hydrocarbon, an ether or a boric acid ester. The use of diluents is generally not necessary, since in the reaction in accordance with the invention hydrocarbons are formed in any case, these hydrocarbons dissolving the various reactants and the substances eing formed.

The pressures used in the process can be chosen as required. It desirable to work at pressure of about 10 atnr,

.nd woll; lg at a pressure of more than 50 atrn. is particular ..cnt inve tion provides as novel compounds N- rocurbon cc-i toes in which at least one of the hydrocarbon radicals cc his two or more carbon atoms, and in particular the co bounds N-t nyl-n-b ;l he N-tri-nb dime hyl-cyclohexy borazane.

The novel compo nds, which can be produced by the process of the in .on, practically always colourless lie,-

which generally no longer smell like amines, if methyl gro sent on the n ogen atom. Exam 1 s which do have methyl groups on the nitrogen atom are N-dirnethyl phenyl borazanc and N-dirn rhyl cyclohexyl bcrazane. The bora' are sensitive to air nd do not react with alkaline or neutral ac, cons Ft only on aciti on that hydrogen is as a i. to novel coit-tzanes do not sublime.

The N-trialkyl borazanes are suitable for reduction purposes in inorganic and especially organic chemistry, in the same way the metal borohydrides. As compared with alkali metal and alkaline earth metal boranates, they have the advantage of not giving such a strong alkaline reaction after reduction has begun. Nevertheless, their reduction power is not less than that of complex metal borohydrides. As compared with the latter, they have the further advantage that they have far better solubility in many organic solvents.

The N-trialkyl borazanes produced by the process of the invention can be purified easily and obtained in an absolutely pure form, generally by dissolution in and recrystallisation frorn hydrocarbons, but preferably by sublimation or distillation. On the Whole, the compounds produced by the process of the invention are, however, so pure that such purification processes are not necessary.

The following examples further illustrate the invention.

aoeaass from trimethylarnine and boron triethyl are placed in a 500 cc. autoclave. After hydrogen has been introduced to give a pressure of 300 atrn., the addition compound is heated with shaking to 180 to 190 C. and left to react at this temperature for hours, the pressure falling to 120 atrn. at room temperature. After the ethane (72 g.) which is formed, has been blown off a colourless solid compound is left in the autoclave and this can be dissolved in and recrystallised from warm hexane. Gas analysis (decomposition of a sample of the substance with dilute acid) of the N-trimethyl borazane purified in this way yields the expected quantity of hydrogen.

EXAMPLE 2 N-Triethyl Borazane (Borine Triethylamine) A mixture of 63 g. (0.346 mol) of boron triisobutyl and 35.2 g. (0.349 mol) of triethylamine is heated in a 200 cc. autoclave with shaking to about 180 C., after hydrogen has been forced in to give a pressure of 320 atrn. Within approximately 5 hours, the pressure has fallen to approximately 95 atrn. at 180 C.; after isobutane has been blown off, fresh hydrogen is introduced to give a pressure of 300 atrn. and the reaction is completed at the same temperature under the conditions indicated. After another 5 hours, the pressure reaches a constant final value (about 70 atrn. at C.). A total of 58 g. of isobutane is collected in a low temperature trap. g. of a colourless, slightly cloudy liquid are .removed from the autoclave. After distillation (B.P.= 100101 C.), N-triethyl borazane is obtained in an analytically pure form with the corresponding hydrogen value (M.P. -4 0).

EXAMPLE 3 N-Dimethyl-Cyclohexyl Borazane (Borine Dimethyl Cyclohexylamine) A mixture of 34 g. (0.345 mol) of boron triethyl and 44 g. (0.345 mol) of dimethyl cyclohexylamine is reacted at 190200 C. for 15 hours in a 300 cc. autoclave with a hydrogen pressure of 300 atrn. The pressure falls to a constant value atrn. at room temperature). After 32 g. of ethane together with the excess hydrogen have been blown off, the autoclave contains a colourless wellcrystallised compound. This compound, even as a crude product, gives a hydride hydrogen content of about of the theoretical by decomposition with dilute sulphuric acid. After being dissolved in and recrystallised from hexane or cyclohexane, the N-dimethyl cyclohexyl borazane is obtainable in a completely pure form (finely developed crystals) with a melting point of 49 C. The

yield is 95% of the theoretical.

EXAMPLE 4 N-Dimethyl-Phenyl Borazane (Borine Dimethyl Aniline) The addition compound of 38 g. (0.388 mol) of boron triethyl and 47 g. (0.388 mol) of dimethyl aniline is heated to 190 C. under a hydrogen pressure of 300 atrn. The fall in pressure is complete after a reaction time of about 15 hours. The ethane (34 g.) which is formed is blown off together with excess hydrogen. The autoclave then contains 46 g. of a yellow-coloured liquid. This can be distilled under reduced pressure, partial decomposition nevertheless taking place. A colourless liquid is obtained,

the hydride hydrogen content of which corresponds to 1 the N-dimethyl phenyl borazane; the yield is between 70 and 80% of the theoretical (NLP. 35 C.).

EXAMPLE 5 834 g. (8.5 mols) of boron triethyl and 870 g. (8.6 mols) of triethylamine are drawn in succession (or in previously mixed form) into an evacuated 5-litre rollertype iron autoclave, a hydrogen pressure of 250 atm. is applied and the substances heated to 220 to 240 while rolling (maximum pressure in this case about 360 atrn.).

4 l After 2-3 hours, the pressure has fallen to about 250 atm. at 220 C. An additional hydrogen pressure of 40 atm. is applied with heating and the reaction is completed at 240 C. in another 2 hours. After the autoclave has been cooled and the gases (excess hydrogen and ethane) have been blown off, N-triethyl borazane is obtained as a colourless liquid which, in a water-jet vacuum, after a small quantity of first runnings (triethylamine) has been drawn off, has a. constant boiling point of -10l C./12 mm. Hg. Yield:960 g. (98% of theoretical); melting point=4 C.

EXAMPLE 6 Cyclohexaue B(HCJPIT)S+ (C2H5)2(l104130)+311;

11 B.N'CC2Hs2(uC4lI9)i-ECaHr A. solution of g. (1 mol) of boron tri-n-pr'opyl and 129 g. (1 mol) of diethyl-n-butylamine irr 100 cc. of cyclohexane is introduced under nitrogen into a cc. autoclave. A hydrogen pressure of 300 atrn. is ap-. plied, whereafter the autoclave is shaken for 5' hours at a temperature of approximately 200 C., the pressure quickly falling. Subsequently, after cooling, the propane which is formed is blown off with the excess hydrogen. The cyclohexane solution of N-dieth -ll-n-butyl horazane is removed and, after the solvent has been distilled off, contains as a colourless residue 140 g. of the liquid bora- Zane, this being a quantitative yield. The compound can be distilled under reduced pressure (13.1 14 mm.=125 C.; melting point 33/32 (3.).

EXAMPLE 7 benzene 6 5)3+ l 9)3l' I2 HsB.N(nCiHs)a+3CsHs A solution of 121 g. (0.5 mol) of boron triphenyl in 250 cc. of benzene is placed in a nitrogen atmosphere in a 750 cc. autoclave. 93 g. (0.5 mol) of tri-n-butylamine is added and a hydrogen pressure of 200 atm. is applied. The clave is then heated to about 200 C., the pressure fading within 4--5 hours to a. constant value (about 30 atm. at room temperature). After the auto clave has been cooled and the excess hydrogen has been blown off, the solution of the N-trin-butyi borwhich is formed can be removed. After the benzene has been distilled olf, finally under reduced pressure, there is obtained a colourless liquid which can be distilled under high vacuum; the yield is practically quantitative (B.P.=87 C.).

EXAMPLE 8 A mixture of 1.4 kg. (10.0 mols) of boron tri-n-propyl and 1.1 kg. (about 11.0 mols) of triethylamine is heated to 200-220in a S-litre autoclave with a stirrer mechanism. A hydrogen cylinder is connected to the autoclave by way of a pressure-reducing valve, so that a hydrogen ressure of about 20 atm. is constantly maintained during the reaction. The reaction is allowed to proceed for approximately 48 hours, the propane formed being removed at intervals through a pressure condenser. 1.1 lag. of T l-triethyl borazane (yield about 95-96% of the theoretical) are obtained, and this compound can be purified by subsequent distillation (33:12 mm.:l00/ 101 C.).

What I claim is:

1. A process for the production of boron compounds having the general formula BII .NR'R"R', wherein R, R" and R represent members selected from the group consisting of saturated lower alkyl, saturated cyclolower alkyl and phenyl radicals, which comprises contacting a boron compound of the general formula R 8, in which R is a lower all-:yl radical with hydrogen under positive pressure under the reaction conditions and at a temperature of from about 120-300 C., in the presence of a tertiary amine NRRR', in which R, R" and R' are as defined above, and recovering the boron compound 2. A process according to claim 1, wherein said contacting is effected at a temperature between 140 and 300 C.

3. A process according to claim 1, wherein said contacting is efiected at a pressure of at least 10 atmospheres.

4. A process according to claim 3, wherein said contacting is effected at a pressure of at least 50 atmospheres.

5. A process according to claim 1 in which said contacting is effected in the presence of an inert solvent.

6. A process according to claim 5, wherein said solvent is selected from the group consisting of saturated aliphatic hydrocarbons, aromatic hydrocarbons, ethers and boric acid esters.

7. A process according to claim 1, wherein the product of the process is purified by dissolution in and recrystallisation from a hydrocarbon.

8. A process according to claim 1, wherein the product of the process is purified by sublimation.

References Cited in the file of this patent UNITED STATES PATENTS Banus et a1. May 18, 1954 Brown Nov. 11, 1958 OTHER REFERENCES Goubeau: Cited in F.I.A.T. Reviews of German Sci ence: Inorganic Chemistry, vol. 1, pages 228 to 229 (1939 to 1946).

Patterson: Chemical and Engineering News, Vol. 34, page 560 (1956). 

1. A PROCESS FOR THE PRODUCTION OF BORON COMPOUNDS HAVING THE GENERAL FORMULA BH3NR''R"R"'', WHERE R'', R" AND R"'' REPRESENT MEMBERS SELECTED FROM THE GROUP CONSISTING OF SATURATED LOWER ALKYL, SATURATED CYCLO-LOWER ALKYL AND PHENYL RADICAL, WHICH COMPRISES CONTACTING A BORON COMPOUND OF THE GENERAL FORMULA R3B, IN WHICH R IS A LOWER ALKYL RADICAL WITH HYDROGEN UNDER POSITIVE PRESSURE UNDER THE REACTION CONDITIONS AND AT A TEMPERATURE OF FROM ABOUT 120-300*C., IN THE PRESENCE OF A TERTIARY AMINE NR''R"R"'', IN WHICH R'', R" AND R"'' ARE AS DEFINED ABOVE, AND RECOVERING THE BORON COMPOUND BH3.NR''R"R"'' THEREBY FORMED. 